Melatonin improves the germination rate of cotton seeds under drought stress by opening pores in the seed coat

Yandan Bai; Shuang Xiao; Zichen Zhang; Yongjiang Zhang; Hongchun Sun; Ke Zhang; Xiaodan Wang; Zhiying Bai; Cundong Li; Liantao Liu

doi:10.7717/peerj.9450

Melatonin improves the germination rate of cotton seeds under drought stress by opening pores in the seed coat

PeerJ. 2020 Jul 6:8:e9450. doi: 10.7717/peerj.9450. eCollection 2020.

Authors

Affiliations

¹ College of Agronomy, HeBei Agricultural University/ State Key Laboratory of North China Crop Improvement and Regulation/ Key Laboratory of Crop Growth Regulation of Hebei Province, Baoding, Hebei Province, China, Baoding, China.
² College of Traditional Chinese Veterinary Medicine, Hebei Agricultrual University, Baoding, China.
³ College of Life Science, Hebei Agricultrual University, Baoding, China.

Abstract

The germination of cotton (Gossypium hirsutum L.) seeds is affected by drought stress; however, little is known about the physiological mechanism affecting germination and the effect of melatonin (MT) on cotton seed germination under drought stress. Therefore, we studied the effects of exogenous MT on the antioxidant capacity and epidermal microstructure of cotton under drought stress. The results demonstrated a retarded water absorption capacity of testa under drought stress, significantly inhibiting germination and growth in cotton seeds. Drought stress led to the accumulation of reactive oxygen species (ROS), malondialdehyde (MDA), and osmoregulatory substances (e.g., proline, soluble protein, and soluble sugars); it also decreased the activity of antioxidant enzymes and α-amylase. Drought stress inhibited gibberellin acid (GA₃) synthesis and increased abscisic acid (ABA) content, seriously affecting seed germination. However, seeds pre-soaked with MT (100 µM) showed a positive regulation in the number and opening of stomata in cotton testa. The exogenous application of MT increased the germination rate, germination potential, radical length, and fresh weight, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), and α-amylase. In addition, MT application increased the contents of organic osmotic substances by decreasing the hydrogen peroxide (H₂O₂), superoxide anion (O₂ ^-), and MDA levels under drought stress. Further analysis demonstrated that seeds pre-soaked with MT alleviated drought stress by affecting the ABA and GA₃ contents. Our findings show that MT plays a positive role in protecting cotton seeds from drought stress.

Keywords: Drought stress; Melatonin; Seed germination; Cotton; Physiology; Testa.

Grants and funding

This work was supported by the National Natural Science Foundation of China (No. 31871569), the Modern Technology System of Agricultural Industry in Hebei (HBCT2018040201, CL), and the Fund of Research Group Construction for Crop Science in Hebei Agricultural University (TD2016C318). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.